1. Field of the Invention
This invention relates to a magnetic head device used for a floppy disk device and, more particularly, to a magnetic head device for floppy disks of high recording density and large memory capacity.
2. Description of the Related Art
In the usual floppy disk device, the magnetic head is in sliding contact with the surface of a rotating floppy disk during writing data on the disk or reading out data from the disk. The magnetic head is provided with a slider for effecting frictional contact with the disk, and a core with a read/write gap for effecting the writing and reading of data is assembled in the slider.
In the floppy disk device of this type, in which the magnetic head is in contact with the floppy disk for the writing or reading, i.e., recording/reproduction, of data, a read/write gap of the magnetic head and the disk surface are desirably found close to each other. If the distance between the magnetic head and floppy disk, i.e., the spacing distance, is large, and recording/reproduction output is reduced.
In the recent floppy disk device, it is reviewed that the revolving rate of the disk is increased so as to increase the data transfer speed. Further, the load urging the head against the disk surface is reduced for suppressing the wear of the disk. With such a device, the rotation of the disk causes air in the neighborhood of the disk surface to enter the space between the disk and slider of the magnetic head. Therefore, the slider tends to separate from the slider surface, or float in the air over the surface, thus reducing the output of the recording/reproduction. In order to solve this problem, Japanese Patent Application Publication Sho 60-55509 discloses that a read/write gap is arranged in a rear portion of the slider (i.e., in the trailing side with respect to the rotation of the disk).
Recently, however, there has been an attempt of increasing the memory capacity by increasing the recording density of a floppy disk. In this disk, the spacing loss is reduced by reducing the surface roughness compared to the prior art. As data concerning this, FIG. 6 shows measurements of the relation between the relative linear velocity and dynamic friction coefficient in various floppy disks with different memory capacities. The graphs of FIG. 6 show measurements with a usual 3.5-inch floppy disk device. Disks A and B are 1MB (2DD) disks, disk C is a 2MB (2HD) disk, and disks D and E have higher density and larger capacity, say 10 MB class, than disks A, B and C. As the surface of these disks, disk A is coarsest, and the surface is smoother in the order of disks B, C, D and E. The "relative linear velocity" is the relative speed between the head and accessed portion of the disk. As is obvious from the figure, the smoother the disk surface the lower the dynamic friction coefficient. This is particularly pronounced when the relative speed is high. This is so because the smoother the disk surface, the more readily a thin layer of the air is formed on the surface, leading to floating of the magnetic head. With a floppy disk device used with a disk having a large memory capacity, the magnetic head is easily floated, or separated from the disk. For this reason, with such device, even if a read/write gap is provided in a rear portion of the slider, the output of the recording/reproduction is reduced. Further, similar problems may arise with a floppy disk device used with a low recording density disk having a comparatively coarse surface if a disk which has been used for long time and has worn surface is used.